I never boil meat unless I want to make stock. It leaches too much flavor. Just grill your sausages low and slow and you will be fine. A trick I have learned is to put the sausages on skewers, it keeps them from curling up and it is easier to turn them and brown evenly all over. But, don't rush them.

i use 2 techniques: 1) for fresh sausage that i know the fat content and origin of (usually homemade or from a friend), i'll grill it on a two level fire starting over the hot side to sear then moving to the low to finish up, this requires a fairly fatty sausage to avoiding drying out (i agree with the other poster that this requires a fair amount of attention - this is why i only do it with a pretty fatty sausage from a source i trust); 2) for leaner sausages/sausage of unkown fat content/from less trusted sources (ie grocery store, etc), i steam it, covered, in about a 1/4" water for 10 minutes then give it some color/crunch/flavor on the grill.

I never boil sausages first. This past weekend, I had some sweet, and some insanely hot sausages on the grill. I cooked on low for a good long time. I used tongs to turn them, so they didn't cause grease flareups. I bet I cooked them for about 40 minutes or so, and they were great. Nicely grilled, cooked thru. Served on grilled rolls with grilled peppers and onions. Great meal for a summers eve.